Electric zinc-furnace with integral condenser.



J. THOMSON.

ELECTRIC ZINC FURNACE WITH INTEGRAL CONDENSER.

APPLIOATION FILED APR.14, 1913.

1,090,428. Patented M21117, 1914.

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ELECTRIC zmc FURNACE WITH INTEGRAL CONDENSER.

APPLICATION FILED APILM, 1913.

' Patented Mar. 17,1914,

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INVENTOR ,iw'nroknm J. THOMSON.v

ELECTRIC ZINC FURNACE WITH INTEGRAL CONDENSER.

' APPLICATION FILED APE.14,'1913. 7 1,090,428.

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Patented Meir. 17 1914.

2' v I nrromvn J. THOMSON.

ELECTRIC ZINC FURNACE WITH INTEGRAL CONDENSER.

APPLICATION FILED APR.1 4, 1913.

Patented Mar. 17, 1914.

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ELECTRIC ZINC FURNACE WITH INTEGRAL CONDENSER. APPLICATION FILED APR.14, 1913.

1090,4285 Patented Mar.17,1914.

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Patented Mar. 17, 191i v J. THOMSON. ELECTRIC ZINC FURNACE WITH INTEGRAL CONDENSER. AITPLIOATIO N FILED APRJA, 1913.

H. .I Q -rlv A I Q HA5 ATTORNEYO" UNITED STATES PATEN OFFICE.

JOHN THOMSON, or NEW YonK, N. Y.-

ELECTBIG ZINC-FURNACE WITH INTEGRAL CONDENSER;

To all whom it may concern Be it known that 1, JOHN THOMSON, a citizen of the United States, and a resident of the borough of Manhattan of the city of New York, in the county and State of New York, have invented certain new and useful Improvements in Electric Zinc-Furnaces with Integral Condensers, of which the following is a specification, reference being made to the accompanying drawings, forming a part hereof.

his invention relates to the metallurgy of zinc, having for its object the production of zinc-fume which is subsequently condensed to liquid metal. I

A description of the particular means for attaining the desired results and such an elucidation of the general principles applicable thereto as will provide a complete disclosure of the invention will be concurrently pointed out in connection with the description of the accompanying drawings, which represent certain embodiments of the invention.

Figure 1 is a transverse but vertical center section, as on the line marked A in Fig. 2. Fig. 2, from its. left handside to its center line, is a longitudinal but vertical section, as on either of the several lines marked B, B of Figs. 1, 3 and 4, while from its center line to its right hand side it is a longitudinal but vertical center section, as on the lines marked C in said Figs. 1, 3 and 4. Fig. 3, from its left hand side to its center line, is a one-fourth horizontal section, as on the plane D of Figs. 1 and 2, and from its center line to its right hand side itis also a one-fourth horizontal section, as on the plane E of said Figs. 1 and 2. Fig. 4 is a half top plan view, as on the line F, of Fig.-

1, and is a View of that-half of the furnace ,which is opposite the half which is shown in Fig. 3. Fig. 5 is a transverse but vertical center section, showing a modlfication 1n portions of the construction. Fig. 6 is a partial plan view of the tube H, Fig. 5. Fig. 7 is a half transverse but vertical center section. of which the opposite side would be similar, showing a modification in portions of the construction. Fig. 8 is a half longitudinal but vertical center section developed from Fig. 7, viewed in either direction. Fig.

9 is a transverse but vertical center section denoting how certain conditions of construction and modified and operation may be reversed and 1g. 10 IS a diagrammatic ele- Specification of Letters Patent. Application filed April 14,

Patented Mar. 17, 1914.

1913. Serial No. 760,915.

vat-ion showing an alternative mode of formmg the resistor.

This furnace is particularly intended for but is not necessarily restricted to the reduction of igneous or commercial oxid of zlnc combined with carbon as the reagent whereby, when adequately heated, substantially the following representative reaction ensues, namely ZnO-l-C Zn-l-CO.

If pure igneous ZnO and C are used in precisely correct relative proportions then the answer of the above formula is an exact expression of the result in that all of the charged material would be volatilized as zinc fume and monoxid of carbon, in which case there would be no residue. Such conditions, however, do not obtain in commercial practice as more or less inert residual matter will remain, depending upon the purity of the materials employed and hence the formula becomes simply representative as above indicated. The presence of this residual matter has hitherto been to some extent a potent cause of difliculty in realizing a successful result.

To avoid explanatory statements which would in fact be in the nature of repetitions, it is prefatorially set forth that this appli cation is more or less correlated with several of the previous applications filed by the present applicant on January 2nd, 1913; but reference may be particularly cited to Serial No. 739,795 thereof.

For decomposing the charge the necessary heat is derived by direct conduction or radiation or by both, from compound resistors, as J, J Fig. 3, ordinarily formed from beds of broken carbon- -hence pervious-interpolated between terminals, as 10, 10 and 12, 12*. 'Theseresistors maybe energized separately or in parallel or in series, but under ordinary circumstances the lat-ter is deemed preferable and this is the method jectin ends of one pair of terminals, as 10, 12, Fig. 4', are connected by copper bus-bars 14, while the opposite terminals 10, 12, are connected to the" lines in the power circuit, as K, Fig. 3.

The reaction takes place at or contiguous to one. of the vertical faces of each resistor, which in cross-section may be somewhat rectangular, its lower narrow side resting upon a suitable refractory sole or hearth, as 15,

illustrated in the drawings. Thus the pro- I 15. These resistors lie parallel each to the other and are sufficiently separated either to provide space for a compound but cooperating condensing system, disposed along the same horizontal plane as that occupied by the said resistors, or a condensing system may be situated along the outside vertical face of each resistor.

The condensing system is generally characterized by several controlling features which may be set forth as follows, namely:

All of the zinc fume condensed to liquid metal is collected in a reservoir or reservoirs underlying the plane of the lower sides of the resistors, while any or all residual gases are discharged at or from the top of the furnace, either between the vertical planes in which the resistors'lie or at the right and left hand sides thereof. The volatilized products of the reaction move in horizontal planes, starting from the" zones of reaction, passing transversely through the interstitial spaces of the resistors and thence entering the primary condensing elements. In front of the exit from the said primary elements is a chamber, shaft, gap or a number of spaces into which the residual gases are primarily received and whereat a primary fall of. temperature is controllably efl'ectuated. Above the said gap or spaces is an expanding chamber which receives the up-flowing gasgs, and this is covered with a laminated roo Vertical faces of the resistors are supplied with charge material as L, from longitudinal side galleries, as M, which may be sub-divided by tiles or bricks m into chutes or pockets N. One of the advantages of such sub-division is that the tiles or bricks may be electrically non-conductive, and

serve, as has been shown in the instance of a resistor charged upon its upper horizontal face, to prevent or minimize the shuntage and flow of current through the charge itself.' This isan advantage of some importance in that the electric conductivity of ZnO rapidly increases with rise in its temperature.

The upper sides or edges of the resistors are covered with bricks 15, upon which a reserve of charge material may be laid, thereby utilizing any heat which may be conducted upwardly. Inert residue which in the ZnO-hC reaction is normally in the form of dust, ash or sinter, will settle down to the bottoms, as 16, of the galleries or pockets, for it is to be borne in mind that there are periods when the charge will-be sufiiciently exhausted, in front of the re sistor faces, to form vertical spaces, which is conducive to .such a residual precipitation. Hence, during certain periods the reaction is carried on by heat radiated from the resistors and, again, by direct conduction of heat.

The residue is occasionally manually withdrawn, as by means of rakes or scrapers, through a series of residue ports, as 17 17, Figs. 1 to 5, formed in the side walls and in line with the bottom of the galleries or pockets. Under certain circumstances, as when an ore containing gangue is to be treated, the residue will be in the form of a liquid slag. In such cases the bottom of the galleries or pockets may be somewhat raised,'as b, Fig. 7 leaving a forward opening an leading to a suit-able trough, as Q, into which the fluidified slag will flow, as denoted by the arrow. As such slags chill or become pasty at rather high temperature, a flue, as P, is provided beneath the trough which may be utilized by fuel, heat or an electric resistor for keeping the slag adequately fluid to be tapped off from end openings not shown. In any event, this method of elfecting the reaction along the vertical face or faces of a'bed of carbon resistor, instead of upon its upper horizontal face, obviates the most serious practical difliculty hitherto encountered in this mode of application of the electric furnace to the metallurgy of zinc, namely: clogging of the resistor, particularly so when the charged materials contain excessive proportions of non-volatilizable matter or gangue.

To conserve the heat that would normally fiow from the lower portion of the resistor into the sole or hearth and thence to the bricks by direct conduction, and also to maintain the inert residual matter hot and friable, and also to maintain any slag at suflicient temperature to prevent it from chilling, special heat insulation may be employed instead of imparting extraneous heat to the slag receiving portions of the furnace which has previously been described. This heat insulation may be provided by forming ducts 18, 18, Figs. 1 and 2, immediately beneath the resistor-sole. These are preferably constructed by using tubes or interlocked or ship-joint bricks, as 19, whereby to obtain the utmost tightness at the joints. The ends are to be closely sealed, as

20. The ducts are to be filled with granu-. lated bricks, infusorial earth, mineral wool,

,or any refractory material in granular,

prisoned air or any gases which may be formed cannot escape, nor can cold replacing alr enter, whereby the desired result is of a high order of effectiveness.

Another particular advantage of this sys-. tem is that every atom of the volatilized products of the reaction, whatever they may be, are necessarily forced to pass through the incandescent body of the resistor in a uniform direction, to a uniform extent and subjected to an approximately uniform temperature which may be maintained so high as to practically eliminate any CO if the conditions are such that it may be primarily formed. And it is a fact that CO may be produced for the reason that thereaction between Z110 and C becomes somewhat active at the relatively low temperature of about 1050 (l, at which both CO and CO may commingle. 'Therefore', while the temperature upon or near to the face of the resistor may be say 130Q C., the reaction will nevertheless be proceeding at diminishing temperatures at certain distances back into the charge. It will now be perceived that when this cold fume and gas pass forward and enter the interstices of the resistor they will be subjected to precisely the same thermal and reactive actionsv as those which primarily pccurred at the higher temperatures. By thus equalizing the quality and temperature of the fume and gas, they are in the most favorable condition for recovery of the one element and expulsion of the other.

In the condensing system the object is to provide a large area of surface over or upon or against which the fume and gas will impinge or come into contact after leaving the resistors, and the temperature of the said surface or the space or spaces thereby inclosed, is to progressively decrease from entrance to exit. Yet the ultimate fall in temperature should be maintainable somewhat above the solidifying or freezing point of zinc.

The functions just set forth can be. realized in the present design of furnace by various means and arrangements, of which selected examples will now be described.

Referring first to Figs. 1 to 4, the zinc re- ('eptaCle 28 is disposed along the longitudinal center of the furnace and in a plane somewhat'below the soles which support the resistors. Rising from each side of the receptacle are two vertical rows OfiPliltQS 24, 24. having numerous openings, as 25, 25, and tied together at their tops by strutpieces, as 26. These plates rest in recesses, Along each of the inner sides of the resistors are a series of spaced uprights which may be of round or square rods. or plates 28, 28 as shown, which serve the purose of supporting a portion of the over-.

head structure and also another purpose yet to he pointpd out. \Vhen constructed in the above manner, three longitudinal chambers are produced, as R, R along each of the inner sides of the resistors, and a central chamber, space or gap S. Chambers and R are to be "filled from their tops with broken carbon, as ,V, Fig. 3, and are then covered with a series of plates, as29, 29 sloping downwardly toward the'gap. These side spaces are designated as filter-chambers,-

and as shown the carbon therein is in contact with the resistors and also with the vertical plates 24, 24*. If the uprights 28, 28, are electrical] non-conductive they will serve the additlonal function, as has been shown in the instance of a horizontal grating, to prevent a direct longitudinal flow of current in the filter carbon; hence the latter will be heated by conduction. The lower surfaces, as 30, 30, of the side chambers, namely those surfaces upon which the filter-beds rest, slope from the resistors downwardly to the reservoir.

Above the filter chambers is a laminated roof formed by a series of plates 31 set toproduce a considerable number of vertical or inclined slots, slits or fissure, as 32, and when these plates are in place a chamb erspace, as Y, is formed between their lower edges and the tops of the filter chamber plates. When the reaction is in progress the volatilized products start from the zones of the reaction, as 33, 33, pass in horizontal planes through the resistors and enter the filter-beds, as indicated by the arrows a. The condensed globules of zinc percolate downwardly through the filtering medium, as indicated by the arrows 0, run along the slopes of the bottoms and fall into the reservoir. The residual gas and also any fume remaining uncondensed pass through the openings in the vertical plates into the central gap, up to the overlying or expanding chamber and thence out through the laminated roof to the atmosphere, as indicated by the arrows 6. -While the operations just described are taking place, any zinc which condenses during the relatively slow flow up through the gap, or in the expansion chamber, or in the fissures of the roof, will necessarily gravitate to the reservoir in the form of a shower or globules which fall into and through any ascending cloud-fume that is entrained with and being carried by the escaping CO.

The heat horizontally conducted by the filter ,beds from the resistors is counterbalanced at the 'gap.- The loss of heat through the overlying plates ofv the filter beds may be controlled by their thickness and the'character of material used. The temperature within the gap is a function of the depth of the roof plates, the character of their material and the temperature to which the CO isreduced at the fissure exits. As a matter of fact, at least a large proportion of the fume will be condensed in the filter beds near to the vertical plates; hence the issuing gases will be. much reduced in volume, that is, by the elimination of fume and reduction due to diminished temperature, and the upward velocity of flow toward-the roof is in a constantly .diminishing ratio amounting to practically a stagnation in or at least a very slow flow from the expansion chamber. Consequently every opportunity, as low velocity, diminished temperature and the element of time, is afforded the metallic fume, which is of the greater density than the rest of the gaseous products of the reaction, to liberate itself from the enveloping gas, thus facilitating the condensation of the metallic fume and the precipitation of the liquid metal resulting therefrom.

The function of the plates, such as 24, 24;, which provided the vertical gap, is particularly one of convenience, as in quickly filling the chambers with carbon or renewing the same as or if exhausted, for they may be dispensed with by simply exercising care in building. up the carbon pieces to thus form the gap walls. On the other hand, the upper filter chamber plates are regarded more essential, as in causing all of the gases to flow horizontally out into the gap and to deflect such zinc as may be condensed in the expansion chamber and the roof directly into the reservoir.

'may escape to atmosphere as such or it may be burned to 00,. In the latter event, especially as the flame would be of large area, its heat may be utilized. Thus, by providing a pan, as 34, suitably supported by spaced bricks, as 35,,and filling it with charge material, the latter may be pre-heated, from whence it can be directly shoveled .into the charging galleries or pockets.

A flue X is shown beneath the zinc receptacle. This is for the purpose of pre-heating the receptacle, as by fuel heat or electrically if filled with "a resistor, or cooling air may be circulated, or non-heat-conducting material may be inserted as needs be.

Referring to Figs. 5 and 6, the left hand side thereof shows the charge material, the resistor and the filter carbon in place. EX- cept in a few particulars this illustration is essentially similar to that of Fig. 1. Thus, instead of the wide gap a flattened tube H of refractory material is inserted along the central axis of the furnace between the filter beds and open to atmosphere at bot-h of its ends. Along the sides of this tube are a number of spaced vertical slabs, as 36, up

'to the outer faces 37, of which the filter bed is laid. The spaces 2' formed by the slabs, the tube and the carbon are for the free downward fall of condensed zinc and the upward flow of gases. The object of the tube is to provide a definite means of controlling the temperature at the two inner vertical faces of the filter beds, either by imparting heat or withdrawing it, according to the requirements of the case. Moreover, in this illustration the depth -of the laminated roof is shownrelatively less than in Fig. 1 and may be covered over with a composite layer of granular carbon and carborundum 38, the latter being atthe top exposed surface. This composite layer 38 acts-as a final filter from which the issuing CO may be burned as a flame in mass to CO Moreover, the depth of the layer may be utilized for controlling the temperature below.

In Figs. 7 and 8 the longitudinal carbon filters are substituted by a series of plates, as 39, separated by blocks or buttons, as lO, to form intervening spaces, slits, slots or fissures 41, whose ends open respectively to the resistors and the central gap. Obviously the tubeH, Fig. 5, might be here utilized ifrequired, as with the filter beds from the resistor toward the center, whereby the zinc condensed therein will roll freely down and drop into .the reservoir. Instead of disposing these plates in a general horizontal direction, they can be set vertically, producing vertical slits, whenthe zinc The plates and slots slope downwardly condensed against the sides thereof would roll down to the sloped bottom and thence.

to the reservoir, but the gases would pass out horizontally to the gap. As the plates in either of the cases just described are not subjected to any material load or stress,

they may be very thin, producing numerous narrow passages and a great aggregate surface through and over whichthe fume and gas must pass. And the foregoing observation equally applies to the roofplates. The aggregate flow-area which may thus be afforded is such as to also insure a low transition of velocity. It will also be noted that square or round rods or tubes of various diameters may readily be stacked, either horizontally or vertically, as a substitute for slabs or plates.

In Fig. 9 a construction is shown which illustrates in many respects a reversal of the conditions of operation described in connection with the construction previously illustrated. According to the embodiment of the invention shown in Fig. 9, a single charging gallery is located in the center between spaced resistors, and the condensing elements are disposed along the outside of said spaced resistors. In this arrangement the primary control of the temperature drop from the issuing slits -11 of the condensing face to the condenser.

plates or lamina 39, the discharge being into the chambers or gaps S, S may be regulated by relatively thin furnace walls, as 42, having'recesses, as 43, into which asbestos board or the like, as 44, may be respectively inserted or removed as the temperature falls below or rises above the determined proper normal temperature. But here the-conditions pertaining to the removal of inert residue are somewhat different. This, however, may readily be providedfor, as for instance, by forming a sump or sumps 45, 45 extending laterally more or less beneath the normal vertical line at the bottom of the resistors. The central rib 46 serves as asupport for the pocket-forming plates 47. The procedure in this case may be to primarily fill the sumps with carbon, then adding on top thereof a layer of ZnO over which will be the normal mixed charge. The consequence thereof will be that more or less of the sump carbon Will'shortly be exhausted, thereby forming a natural recess into which the ash'y,

residue will accumulate, also filling the spaces in any of the residual carbon. Moreover, such residue can readily be poked down into the carbon and the sumps. The ultimate removal of the residue at considerable intervals of time may be through end openings in the furnace walls, not shown, or by withdrawing the pocket plates and scooping it out from above.

By referring to Figs. 1, 5, 7 and 9 it will readily be perceived that the compound elements are separately operative either as distinct units or astportions of a unit in which all are contained, but such would be.with sacrifice of features which are regarded as advantageous.

As is shown in the diagrammatic Fig, 10, the resistors need not necessarily be formed of beds of broken carbon, as so-called rod resistors may here be employed, the-inter- ,vening transverse spaces affording (free pas sageof the fume and gas from The various figures of the drawings have been laid out to a uniform scale, but the said scale does not necessarily represent actual working dimensions or complete details in that the object has been rather to denote a schematic embodiment of principles which to those skilled in the art will doubtless be sufficient to realize the generic scope and spirit of the invention.

Finally, it may not be inept to briefly summarize the general advantages of'this design in so far as relates to 1t -S adaptable flexibility to various commercial and socalled practical conditions.

Thus, if the resistance and consequent heat development of one resistor becomes greater than the other, this can readily be corrected by deft packing or poking of thecarbon or the charge or both, or one of the other of the reaction the top of the condenser.

the resistors may be temporarily out out of serv ce; all. portions of the reaction and also of the condensing spaces are readily accessible even when their temperature is rather high; the dimension of the furnace in plan may equal or approximate a square which usually presents from 20% to 30% less radiating surface to atmosphere than in the instance of rectangular forms; the in troduction of pyrometers can be numerously and most conveniently made from above without piercing the inclosing walls; the

ohmic resistance of the resistors can readily be adapted to meet the various voltages of standard apparatus; the runs may be of long duration; the materials of construction are regular; the normal temperatures to be dealt with are relatively low; the conservation of developed energy is of a high order, and the reaction, due to the low fume and gas velocities and diminution of obstruct-ion to flow, may proceed with all the said resistors OPP site to'those at which the.

reaction takes place.

'3. An electric zinc furnace having a porous resistor or resistors, a parallel con-' denser or condensers, all being disposed along the same horizontal plane, a zinc reservoir or reservoirs situated in an underlylng plane, and a gas exit or exits in or at 4. An electric zinc furnace and an integral condensing system comprising in combination the -following elements: parallel longitudinally-extending electrically energized carbon resistors formed so that fume can" flow therethrough, and condensing chambers which are arranged to receive fume after it has passed through the resistors, the charge receiving portion being arranged so that the reaction takes place along vertical f aces' of said resistors and the volatilizedproducts thereof pass laterally through the resistors, thence entering the condens ers in horizontal planes, while the inert residue precipitates toward the bottoms of the reaction zones. V

5. In an electric zinc furnace, parallel porous resistors, galleries or pockets arranged to supply charge material to one of each of the vertical faces of said resistors, condensing chambers containing broken carbon', members disposed along verticalsides of said resistors opposite the zones of reaction which members are constructed and arranged so as to permit the fume to flow from the resistors to the interior of the condensing chambers, the condensing chambers being provided with a space or gap for receiving the residual gases, with an overlying chamber from whence the,s a1d gases pass to atmosphere, and also with an underlying receptacle for receiving liquid metal.

6. In an electric zinc furnace, a condensing chamber lying parallel to a resistor from whence'the fume and gas are received in horizontal planes, the reaction proceeding along or in front of the opposite vertical face of. said resistor.

7. In an electric zinc furnace, parallel resistors, receptacles arranged to supply charge materials to vertical faces of said resistors, condensing systems parallel to the resistors but on sides thereof opposite the reaction zones, and a vertical space, chamber or gap into which flow the residualgases issuing from the condensing systems, and whose temperature relative to that of the reaction zones is controllable.

8. In an electric zinc furnace, an integral condensing chamber or chambers containing broken carbon, spaced condensing members, from between which. liquid metal re sulting from the condensation of metallic fume gravitates to an underlying reservoir, the residual gases issuing horizontally and thereafter deflecting and flowing upwardly.

9. In an electric zinc furnace, a vertical space or gap which receives in a horizontal direction the residual gases from primary condensing means, thence discharging the said gases into an expanding chamber whose roof is composed of spaced plates.

10. In an electric zinc furnace, a condens-- ing chamber whose roof is formed by plates between which residual gases can pass.

11. In an electric zinc furnace, a chamber containing a condensing system whose roof is formed of spaced plates, the spaces being approximately vertical.

12. In an electric zinc containing a condensing system, an inclosing porous roof and a superimposed pan or plate for receiving a reserve of charge materials to be pre-heated by burning the issuing CO to CO 13. In an electriczinc furnace having a resistor through which the volatilizedprodnets of the reaction pass laterally into and through means providing a filter, the residual gases issuing from a vertical face of the filter, and means for controlling the drop of temperature between the said vertical face and the resistor.

14. In an electric zinc furnace, a resistor furnace, a chamber charge receiving means, and constructed so that the reaction takes place along a vertical face of said resistor and so that the inert residual ash or sinter collects at the floor of said gallery or pockets, the furnace walls being provided with a plurality of ports which are disposed transversely to said resistor and through which the said residue may be broken up and removed.

16. An electric zinc furnace l'lilViIlg a bed of carbon resistor paralleled by a contiguous 1 receiving and charging means, said means being arranged so that the reaction takes place along a vertical face of said resistor, the furnace being provided with a sump,

which sump is partially-covered .so .as to leave a narrow or slit-like opening located near to the lower portion of said resistor, through which liquefied slag may flow into said sump.

17. In an electric. zinc furnace, a bed of carbon resistor paralleled by a bed of carbon filter and a plurality of spaced plates, electrically non-conductive, transversely disposed in said filter bed, whereby to prevent a longitudinal flow therein of current derived or shunted from the resistor.

18. An electric zinc furnace having parallel resistors between which charge material is supplied and in which furnace the reaction takes place along the opposing vertical faces of said resistors, a sump or sumps formed in the bottom of the intervening gap and a filling of broken carbon serving to primarily support the charge material, but upon or into which the ash or sinter ultimately precipitates and collects.

19. An electric zinc furnace having an integral condensing system in which portions of the fume may be condensed in an up-flow space or gap, in an expanding chamber, in a laminated roof and in broken carbon on top of said roof, the condensing system being provided with a series of sloping plates forming the bottom of said expanding chamber, upon which sloping plates the liquid zinc resulting from the condensing of the fume impinges, runs down and thence falls through the said gap into an underlying collecting reservoir, with which the condensing system is also provided.

20. An electric zinc furnace having a bed comprising a parallel condensing chamber filled with filter carbon, and a series of outer vertical plates having transverse openings for the escape of gases, the said plates serving to vertically support that portion of the filter carbon farthest from the resistor.

21. In an electric zinc furnace, abed of carbon resistor supported by a Y sole or hearth, an underlying duct with sealed ends and loose and uncompressed granular or fibrous non-heat-conducting material packed in said duct.

22. In an electric zinc furnace, compound parallel resistors with interposed condensing chambers filledwith filter carbon, two series of outer plates having transverse openings for the escape of gases, and spaced thrust pieces between thetwo sets of plates, the said plates serving to support those portions of the filter carbon farthest from the resistors.

23. An electric zinc furnace having com- I pound parallel resistors and parallel spaces removable bricks, tiles or or supplying charge material and containing integral condensing chambers, all being disposed along the same horizontal plane,

said furnace comprising a plurality of free mally inclosing the tops of t e resistorsand the condensing chambers, but which maybe removed for theremoval of the resistor or the filter carbon or for the renewal thereof.

24:. In a combined zinc furnace and condenser, a receiving pan located above the condenser and arranged so that it is heated by the ignition of the residual gaseous products of the reaction which pass from the condenser, whereby the furnace charge may be preheated prior to its bein received into the reaction chamber of the urnace.

25. In a combined furnace and condenser, 21. receiving pan located above the furnace lates for norreaction chamber, which pan is heated by the ignition of the residual gaseous products leaving the condenser.

26. A combined zinc furnace and con-' denser having a longitudinally extending broken carbon resistor provided on opposite sides thereof with spaced resistor retaining plates.

27. In a combined zinc furnace and condenser, a longitudinally extending carbon resistor provided on opposite sides with spaced transversely but vertically extending plates, the furnace charge being received at one side of the resistor between the plates, and the space at the other side of the resistor between the plates being filled with broken carbon.

28. In a combmed zlnc furnace and condenser, a broken carbon resistor having a reaction chamber located at one side thereof, and at the other side thereof a condensing chamber provided with transversely extending spaced resistor retaining plates.

29. In a combined furnace and condenser,

a longitudinally extending resistor having at one side thereof a charge receivlng chamber and at the other side thereof a condensing chamber provided with a floor slanting downwardly from the resistor to a sump for receiving liquid zinc resulting from the condensation of zinc fume.

30. In a zinc furnace a longitudinally ex tending resistor and adjacent thereto a longitudinally extending duct provided therein withheat insulating material.

This specification signed and witnessed this 12th day of April, 1913.

- OHN THOMSON.

G. MCGRANN. 

